8252399: Update mapMulti documentation to use type test pattern inste…

…ad of instanceof once JEP 375 exits preview

Reviewed-by: dfuchs, psandoz, smarks

src/java.base/share/classes/java/util/stream/Stream.java

@@ -340,6 +340,8 @@ public interface Stream<T> extends BaseStream<T, Stream<T>> {
      */
     DoubleStream flatMapToDouble(Function<? super T, ? extends DoubleStream> mapper);
 
+    // THE EXAMPLES USED IN THE JAVADOC MUST BE IN SYNC WITH THEIR CORRESPONDING
+    // TEST IN test/jdk/java/util/stream/examples/JavadocExamples.java.
     /**
      * Returns a stream consisting of the results of replacing each element of
      * this stream with multiple elements, specifically zero or more elements.
@@ -386,8 +388,8 @@ public interface Stream<T> extends BaseStream<T, Stream<T>> {
      * <pre>{@code
      *     Stream<Number> numbers = ... ;
      *     List<Integer> integers = numbers.<Integer>mapMulti((number, consumer) -> {
-     *             if (number instanceof Integer)
-     *                 consumer.accept((Integer) number);
+     *             if (number instanceof Integer i)
+     *                 consumer.accept(i);
      *         })
      *         .collect(Collectors.toList());
      * }</pre>
@@ -397,8 +399,8 @@ public interface Stream<T> extends BaseStream<T, Stream<T>> {
      * <pre>{@code
      * class C {
      *     static void expandIterable(Object e, Consumer<Object> c) {
-     *         if (e instanceof Iterable) {
-     *             for (Object ie: (Iterable<?>) e) {
+     *         if (e instanceof Iterable<?> elements) {
+     *             for (Object ie : elements) {
      *                 expandIterable(ie, c);
      *             }
      *         } else if (e != null) {
@@ -407,8 +409,8 @@ public interface Stream<T> extends BaseStream<T, Stream<T>> {
      *     }
      *
      *     public static void main(String[] args) {
-     *         Stream<Object> stream = ...;
-     *         Stream<Object> expandedStream = stream.mapMulti(C::expandIterable);
+     *         var nestedList = List.of(1, List.of(2, List.of(3, 4)), 5);
+     *         Stream<Object> expandedStream = nestedList.stream().mapMulti(C::expandIterable);
      *     }
      * }
      * }</pre>

test/jdk/java/util/stream/examples/JavadocExamples.java

@@ -0,0 +1,72 @@
+/*
+ * Copyright (c) 2021, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+import org.testng.annotations.Test;
+
+import java.util.List;
+import java.util.function.Consumer;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+import static org.testng.Assert.assertEquals;
+
+/*
+ * THE CONTENTS OF THIS FILE HAVE TO BE IN SYNC WITH THE EXAMPLES USED IN THE JAVADOC.
+ *
+ * @test
+ * @run testng/othervm JavadocExamples
+ * @summary Checks to ensure example code displayed in the API documentation of
+ *  java/util/Stream compiles correctly.
+ */
+public class JavadocExamples {
+
+    // From mapMulti
+    @Test
+    public void testNumberIntegerExample() {
+        Stream<Number> numbers = Stream.of(1, 2, 3.0);
+        List<Integer> integers = numbers.<Integer>mapMulti((number, consumer) -> {
+            if (number instanceof Integer i)
+                consumer.accept(i);
+        })
+        .collect(Collectors.toList());
+
+        assertEquals(integers, List.of(1,2));
+    }
+    @Test
+    public void testExpandIterableExample() {
+        var nestedList = List.of(1, List.of(2, List.of(3, 4)), 5);
+        Stream<Object> expandedStream = nestedList.stream().mapMulti(C::expandIterable);
+
+        assertEquals(expandedStream.toList(), List.of(1,2,3,4,5));
+    }
+    static class C {
+        static void expandIterable(Object e, Consumer<Object> c) {
+            if (e instanceof Iterable<?> elements) {
+                for (Object ie : elements) {
+                    expandIterable(ie, c);
+                }
+            } else if (e != null) {
+                c.accept(e);
+            }
+        }
+    }
+}